Patent application title: RESONATOR ELEMENT AND OSCILLATOR

Abstract:

A resonator element includes: a resonating body having a first region and
a second region, the first region receiving a compression stress or an
extension stress by a vibration, the second region receiving an extension
stress responding to the compression stress in the first region, or a
compression stress responding to the extension stress of the first
region; and at least one film layer, on a surface of the resonating body
between the first and the second regions, having thermal conductivity
higher than thermal conductivity of the resonating body. In the element,
the film layer includes a recessed section in which at least one film
layer is removed between the first and the second regions.

Claims:

1. A resonator element, comprising:a resonating body having a first region
and a second region, the first region receiving a compression stress or
an extension stress by a vibration, the second region receiving an
extension stress responding to the compression stress in the first
region, or a compression stress responding to the extension stress of the
first region; andat least one film layer, on a surface of the resonating
body between the first and the second regions, having thermal
conductivity higher than thermal conductivity of the resonating
body,wherein the film layer includes a recessed section in which at least
one film layer is removed between the first and the second regions.

2. the resonator element according to claim 1, wherein the resonating body
includes a groove section having the recessed section.

3. The resonator element according to claim 1, wherein the resonating body
vibrates in a flexural vibration mode.

4. An oscillator comprising the resonator element according to claim 1.

Description:

BACKGROUND

[0001]1. Technical Field

[0002]The present invention relates to prevent a lowering of Q value due
to thermal conduction, particularly of a resonator element and an
oscillator.

[0003]2. Related Art

[0004]Tuning fork type piezoelectric resonator elements have been widely
used. In such tuning fork type piezoelectric resonator element, a pair of
resonating arms vibrates to be closer to each other and apart from each
other. Vibration energy losses generated in the flexural vibration of the
tuning fork type resonator element cause a resonator to deteriorate the
performances. For example, an increase of a CI (crystal impedance) value
or a decrease of a Q value occurs. Thermal conduction is considered as
one factor of the vibration energy losses.

[0005]FIG. 7 is an explanatory view of the thermal conduction of a
piezoelectric resonator element. As shown in FIG. 7, a piezoelectric
resonator element 1 includes two resonating arms 3 and 4 extending from a
connecting section 2 in parallel. When a predetermined voltage is applied
to exciting electrodes (not shown) in this state, the resonating arms 3
and 4 vibrate. In a vibration state in which the resonating arms 3 and 4
vibrate to be apart from each other, a compression stress is applied
around root portions shown as shaded regions A at the outsides of the
resonating arms 3 and 4. In contrast, an extension stress is applied
around root portions shown as shaded regions B at the inner sides of the
resonating arms 3 and 4.

[0006]In a vibration state in which the resonating arms 3 and 4 vibrate to
be closer to each other, an extension stress is applied to the shaded
regions A while a compression stress is applied to the shaded regions B.
In the regions to which the compression stress is applied, the
temperature increases while in the regions to which the extension stress
is applied, the temperature decreases. The thermal conduction generated
between the compression portions receiving the compression stress and the
extension portions receiving the extension stress of the resonating arms
that vibrate in a flexural mode causes the vibration energy losses.
Lowering of the Q value caused by the thermal conduction is called a
thermoelastic loss.

[0007]In order to prevent or suppress the lowering of the Q value due to
the thermoelastic loss, a tuning fork type resonator is disclosed that
includes vibrating arms each having a rectangular section and a groove or
a hole formed on the centerline thereof, in JP-UM-A-2-32229, for example.

[0008]The JP-UM-A-2-32229 describes that the Q value, which shows the
thermoelastic loss, becomes minimum at fm=1/2πτ where fm is a
relaxation frequency, and τ is a relaxation time, in a resonator
vibrating in a flexural mode. This is derived from a stress-strain
relation equation that is well known in a case of internal friction,
which is generally caused by temperature difference, of a solid. The
relation of the Q value and the frequency is generally shown as a curve F
in FIG. 8. In the figure, a frequency at which the Q value is a minimum
Q0 is a thermal relaxation frequency f0(=1/2πτ). A region of
higher frequency (1<f/f0) is referred to as an adiabatic region while
a region of lower frequency (f/f0<1) is referred to as an isothermal
region where "f/f0=1" is a reference point.

[0009]Incidentally, a flexural resonator element is disclosed, for
example, in JP-A-2005-39767 as a tuning fork type flexural resonator
having a frequency of a fundamental mode vibration with high frequency
stability, and a high Q value. FIGS. 9A and 9B show schematic structures
of the flexural resonator element in related art. FIG. 9A is a plan view.
FIG. 9B is a cross sectional view taken along the line A-A of FIG. 9A. A
flexural resonator element 100 includes tuning fork arms 102 and a tuning
fork arm base section 104. The tuning fork arm 102 has grooves 106 at the
upper and lower surfaces. Electrodes 110 and 112 are provided to the side
surfaces of the grooves 106. Electrodes 114 and 116 having different
polarities are provided to the side surfaces of the tuning fork arms 102.
The electrodes provided the side surfaces of the grooves are faced to
each other with the piezoelectric body interposed therebetween, and
likewise the electrodes provided to the side surfaces of the tuning fork
arms are faced to each other with the piezoelectric body interposed
therebetween.

[0010]In the structure disclosed in the JP-A-2005-39767, a heat transfer
path between a compression region and an extension region of the tuning
fork arms 102 is narrowed by the grooves 106 on the way as shown in FIG.
9B. As a result, a relaxation time τ, which is a period during which
the temperatures of the compression region and the extension region come
to an equilibrium state, lengthens. As can be seen in an adiabatic region
of FIG. 8, the curve F is shifted to a position of a curve F1 in a lower
frequency side as a result of forming the grooves 106. In this shift, the
relaxation frequency is lowered and the shape of the curve F is not
changed. Accordingly, the Q value increases as shown with an arrow "a".
On the other hand, the curve F is shifted to a position of a curve F2
when electrodes are formed. The Q value decreases as shown with an arrow
"b". The reason of the shift can be considered that the electrodes form a
heat transfer path. A material having conductive property, such as an
electrode material, has large thermal conductivity. In the conductive
material, thermal energy is carried by electrons in addition to phonons
of metal. As shown in FIG. 9B, thermal conduction is achieved through the
electrodes in addition to the material, i.e., quartz crystal, shortening
the relaxation time τ to increase the relaxation frequency. As a
result, it can be considered that the curve F is shifted to the position
of the curve F2 in a higher frequency side.

SUMMARY

[0011]An advantage of the invention is to provide a resonator element that
can prevent the lowering of a Q value due to thermal conduction, and an
oscillator in which the resonator element is mounted.

[0012]The present invention is intended to solve at least part of the
mentioned problems and can be implemented by the following aspects of the
invention.

[0013]According to a first aspect of the invention, a resonator element
includes a resonating body having a first region and a second region, the
first region receiving a compression stress or an extension stress by a
vibration, the second region receiving an extension stress responding to
the compression stress in the first region, or a compression stress
responding to the extension stress of the first region; and at least one
film layer, on a surface of the resonating body between the first and the
second regions, having thermal conductivity higher than thermal
conductivity of the resonating body. The film layer includes a recessed
section in which at least one film layer is removed between the first and
the second regions.

[0014]In the resonator element, a part of the film formed on the surface
of the resonating body is removed between the first and the second
regions both of which alternately receive the compression stress and the
extension stress when the resonator element vibrates. The heat transfer
path between the compression region and the extension region is, thus,
restricted, lengthening the relaxation time. As a result, the relaxation
frequency is lowered. This lowering of the relaxation frequency enables
the lowering of the Q value due to the thermal conduction to be
prevented, attaining a high Q value.

[0015]The resonating body may include a groove section having the recessed
section.

[0016]The formation of the groove section lengthens the relaxation time,
which is a period during which the temperatures of the compression region
and the extension region come to an equilibrium state. As a result, the
relaxation frequency is lowered. This lowering of the relaxation
frequency enables the lowering of the Q value due to the thermal
conduction to be prevented, attaining a high Q value.

[0017]The resonating body may vibrate in a flexural vibration mode.

[0018]As a result, the lowering of the Q value due to thermal conduction
associated with the compression and extension stresses caused by the
flexural vibration can be prevented, attaining a high Q value.

[0019]According to a second aspect of the invention, an oscillator
includes the resonator element of the first aspect.

[0020]As a result, the oscillator can be provided that includes the
resonator element described above and prevents the lowering of the Q
value due to the thermal conduction.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021]The invention will be described with reference to the accompanying
drawings, wherein like numbers reference like elements.

[0022]FIG. 1 is a schematic view illustrating a structure of a resonator
element of a first embodiment of the invention.

[0023]FIG. 2 is a cross sectional view of the resonator element taken
along the line A-A of FIG. 1.

[0024]FIG. 3 is a cross sectional vies illustrating a featured part of a
resonator element according to a second embodiment of the invention.

[0025]FIG. 4 is a cross sectional vies illustrating a featured part of a
resonator element according to a third embodiment of the invention.

[0026]FIGS. 5A and 5B are cross sectional views illustrating a featured
part of a resonator element according to a fourth embodiment of the
invention.

[0027]FIG. 5A shows that recessed sections are each provided to the upper
layer of the first exciting electrode.

[0028]FIG. 5B shows that recessed sections are provided in each of which
the upper and the lower layers of the first exciting electrode is
removed.

[0029]FIG. 6 shows an oscillator in which the resonator element of the
invention is mounted.

[0030]FIG. 7 is an explanatory view of thermal conduction of a
piezoelectric resonator element.

[0031]FIG. 8 shows a relation of a relaxation frequency and the minimum
value of a Q value.

[0033]A resonator element and an oscillator of the invention are described
below in detail with reference to the accompanying drawings. In the
following embodiments, a tuning fork type piezoelectric resonator element
is described as an example of the resonator element. The resonator
element of the invention, however, is not limited to the tuning fork type
piezoelectric resonator element. The invention can be applied to any
resonator elements as long as they produce temperature increasing
portions and temperature decreasing portions so as to be responded to
each other when they are vibrated. The resonator element is not limited
to a piezoelectric body. The vibration mode is also not limited to a
flexural vibration mode. FIG. 1 is a schematic view illustrating a
structure of a resonator element of a first embodiment of the invention.
FIG. 2 is a cross sectional view taken along the line A-A of FIG. 1.

[0034]A resonator element 20 includes a base section 22, a pair of
resonating arms 24 extending from the base section 22, and a pair of
supporting arms 32, as shown in FIG. 1. In the first embodiment, the
resonator element 20 is made of quartz crystal. Examples of the material
for the resonator element 20 can include piezoelectric materials such as
lithium tantalite, lithium niobate, and lead zirconium titanate,
semiconductor materials such as silicon semiconductor, and insulative
materials, in addition to quartz crystal.

[0035]The resonating arm 24 serving as a resonating body has a root
portion at which it is connected to the base section 22. In the root
portion, the width is widened toward a side adjacent to the base section
22. The resonating arm 24 is, thus, connected to the base section 12 with
a large width, resulting in having high rigidity. As shown in FIG. 2,
long grooves 30 are formed as a groove section on first and second
surfaces of the resonating arm 24 in the long side direction of the
resonating arm 24. The long groove 30 functions to reduce thermal elastic
losses, enhancing the resonating arms being efficiently vibrated. As a
result, electric field efficiency is improved, i.e., improvement of
excitation efficiency, to lower a CI value.

[0036]The supporting arms 32 extend in a direction intersecting (e.g.,
perpendicular to) a direction in which the pair of resonating arms 24
extend from the base section 22. The supporting arms extend in opposite
directions to each other and bend, and further extend in the extending
direction of the pair of resonating arms 24. This bending allows the
supporting arms 32 to be formed in compact. The supporting arms 32
function as portions attached to a package (not shown), for example. As a
result of being attached with the support arms 32, the resonating arms 24
and the base section 22 come to be in a state of floating in the package.
In the embodiment, the supporting arms 32 are disposed at the both sides
of the two resonating arms 24 so as to sandwich them. The structure,
however, is not limited to this. At least one of the supporting arms 32
may be disposed between the resonating arms 24.

[0037]The base section 22 has a pair of cut-in sections 38 formed in a
direction so as to be faced to each other. The pair of cut-in sections 38
is formed to the base section 22 each at a location closer to the
resonating arm 24 than a part to which the supporting arm 32 is
connected. The cut-in sections 38 cancel out most of the vibrations of
the resonating arms 24 being transmitted and suppress the vibrations from
being transmitted to an outside through the base section 22 and the
supporting arms 32 (vibration leak). As a result, an increase of a CI
value can be prevented.

[0038]The resonating element 20 has an electrode 40 thereon. The electrode
40 includes a first electrode 42 and a second electrode 44. The first
electrode 42 and the second electrode 44 are electrically isolated from
each other in order to be coupled to different potentials. The electrode
40 is composed of two layers, for example. One is an under layer (e.g., a
Cr layer) that has a high adhesiveness with a piezoelectric body, and the
other formed on the under layer is a layer (e.g., an Au layer) that has a
low electric resistance and is hardly oxidized.

[0039]Table. 1 shows thermal conductivities of film materials for forming
the resonator element. Here, besides the electrode 40, other films, such
as a protective film, and an adjustment film, and a driving material may
be formed on the resonator element 20.

[0040]The film material of the invention has thermal conductivity higher
than the thermal conductivities of quartz crystal used for the resonating
body. The thermal conductivities of quartz crystal are: 6.2
Wm-1K-1 (in crystal X-axis direction or crystal Y-axis
direction); and 10.4 Wm-1K-1 (in crystal Z-axis direction).
Examples of the film material include Ag, Al, Au, C (diamond), Cr, Cu,
Mo, Ni, Si, Ti, Pt, AlN, and ZnO. In a case where a number of films are
layered on the surface of the resonator element 20, the films are formed
in a manner such that an upper layer has thermal conductivity higher than
that of the underlayer thereof. In a case where a material other than
quartz crystal is used for the resonating body, a film material having
thermal conductivity higher than that of the material is used for forming
a film.

[0041]First exciting electrodes 46 are formed inside the long grooves 30
(at the inner side surfaces and the bottom surfaces) of each resonating
arm 24. Specifically, the long grooves 30 are respectively formed on a
first surface and a second surface (a front surface and a rear surface)
of each resonating arm 24. A pair of the first exciting electrodes 46 is
each formed inside one of the long grooves 30 back to back. The first
exciting electrode 46 formed inside the long groove 30 at the first
surface may be formed in a manner such that the first exciting electrode
46 extends on the first surface. The first exciting electrode 46 formed
inside the long groove 30 at the second surface may be formed in a manner
such that the first exciting electrode 46 extends on the second surface.
The pair of the first exciting electrodes 46 is electrically coupled. The
pair of the first exciting electrodes 46 formed on one resonating arm 24
is electrically coupled to second exciting electrodes 48 on the other
resonating arm 24.

[0042]The second exciting electrodes 48 are formed on the side surfaces of
each resonating arm 24. Specifically, a pair of the second exciting
electrodes 48 is formed on both the side surfaces back to back of each
resonating arm 24. The side surfaces are connected to the first and the
second surfaces and formed in the thickness direction of the resonating
arm 24 so as to face opposite directions. Each of the second exciting
electrodes 48 may be formed in a manner such that the second exciting
electrode 48 extends to on at least one of (or both) the first and the
second surfaces. The pair of the second exciting electrodes 48 is
electrically coupled to a connection electrode 50 formed on at least one
of (or both) the first and the second surfaces at a portion (e.g., the
end section), on which the long groove 30 is not formed, of the
resonating arm 24.

[0043]The first excitation electrode 46 formed on one resonating arm 24 is
electrically coupled to the second excitation electrode 48 formed on the
other resonating arm 24 through a lead-out electrode 52 on the base
section 22. The lead-out electrode 52 is formed up to the supporting arm
32 arranged adjacent to the resonating arm 24 where the second excitation
electrode 48 is formed. The lead-out electrode 52 may be formed on the
first and the second surfaces (or further on the side surfaces) of the
resonating arm 32. In this case, the lead-out electrode 52 can serve as a
part electrically coupled to an outside on the resonating arm 32. The
first electrode 42 is composed of a set of the first exciting electrode
46, the second exciting electrode 48, the connection electrode 50, and
the lead-out electrode 52 that are electrically coupled. Likewise, the
second electrode 44 is composed of another set of the first exciting
electrode 46, the second exciting electrode 48, the connection electrode
50, and the lead-out electrode 52 that are electrically coupled. Each
resonating arm 24 includes the first electrode 42 and the second
electrode 44. Applied a voltage between the first exciting electrode 46
and the second exciting electrode 48, the resonating arm 24 is vibrated
since the side surfaces are expanded and contracted.

[0044]The first exciting electrode 46 formed inside the long groove 30 has
a layered structure of Cr serving as a lower layer and Au serving as an
upper layer as described above, in the embodiment. The first exciting
electrode 46 includes a recessed section 60 in which an Au film of the
upper layer is removed as shown in FIG. 2. It is advisable that the
recessed section 60, while which is formed along the long groove 30 as
shown in FIG. 1, is formed at least between a compression region and an
extension region, i.e., at the root portion of the resonating arm 24. In
a case where films are layered on the resonator element 20, the upper
layer made of a material having high thermal conductivity is removed.

[0045]Here, the resonator element 20 of the invention aims to be used in a
high frequency range in which thermal elastic loss is adiabatic. In the
range, a relation of 1<fr/f0 is satisfied where fr is the mechanical
resonance frequency of a resonating body and f0 is the thermal relaxation
frequency of the resonating body alone. Here, the term "resonating body
alone" means a resonating body on which metal films, such as electrodes,
are thoroughly not provided. For example, quartz crystal is used as a
material for a resonator element, the resonator body alone means a
resonator made of using quartz crystal only, and having no materials
provided thereon.

[0046]Here, it is also known that the relaxation frequency f0 can be
obtained from the following formula.

f0=πk/(2ρCpa2) (1)

Here, π denotes circle ratio, k denotes a thermal conductivity in
vibration direction of the resonating arm, ρ denotes a mass density
of the resonating arm, Cp denotes a heat capacity of the resonating arm
and a denotes a width of the resonating arm.

[0047]The resonator element 20 thus structured of the invention is
electrically coupled to connection electrode of a package with the
exciting electrodes and fixed. Applied a predetermined voltage to the
exciting electrodes in this state, the resonating arms 24 vibrate to be
closer to and apart from each other in a flexural vibration mode. The
resonating arm 24 becomes a resonating body when it is vibrated. The
resonating arm 24 includes a first region in which the resonating arm 24
receives a compression stress or an extension stress, and a second region
in which the resonating arm 24 receives an extension stress when the
first region receives the compression stress and a compression stress
when the first region receives the extension stress.

[0048]The flexural vibration causes a compression stress and an extension
stress to occur at the root portion of the resonating arms 24. When the
resonating arms 24 bend to be closer to each other, a compression stress
is applied to the inner sides (e.g., the first region) of the root
portion while an extension stress is applied to the outer sides (e.g.,
the second region) of the root portion. Resulting mechanical strains
cause a part to which the compression stress is applied to rise the
temperature while a part to which the extension stress is applied to
decrease the temperature. In contrast, when the resonating arms 24 bend
to be apart from each other, an extension stress is applied to the inner
sides of the root portion to decrease the temperature while a compression
stress is applied to the outer sides to increase the temperature. In this
way, there is a temperature gradient between the inner side and the outer
side at the root portion of the resonating arm 24. The gradient is
reversed between when the resonating arms 24 bend to be closer to each
other and when they bend to be apart from each other.

[0049]In a case shown in FIG. 2, heat is transferred from the compression
region to the extension region through the long groove 30 due to the
temperature gradient. In this case, a heat transfer path from the
compression region to the extension region is narrowed on the way by the
long groove 30. As a result, a relaxation time τ, which is a period
during which the temperatures of the compression region and the extension
region come to an equilibrium state, comes to longer than a relaxation
time τ0, which is the relaxation time of a structure having no long
groove 30. Because above case can be considered as an equivalent case in
which a width T of the long groove 30 is extended, along the width
direction of the resonating arm 24, to a virtual width T1 shown in FIG. 2
with broken lines. Further, the first exciting electrode 46 formed inside
the long groove 30 includes the recessed section 60 in the upper layer of
Au in the embodiment. The recessed section 60, thus, cuts off the heat
transfer path passing through Au having high thermal conductivity. This
structure causes longer relaxation time, resulting in the relaxation
frequency being lowered based on the equation of fm=1/2πτ.

[0050]The lowering of the relaxation frequency is described based on FIG.
8 showing the relationship between a frequency and a Q value. In FIG. 8,
the shape of the curve F is not changed, but the curve F is shifted to a
position of the curve F1 in a lower frequency side, with the lowering of
the relaxation frequency. Accordingly, if a desired use frequency is in
the adiabatic region, the Q value is always higher than the minimum value
Q0 in the conventional structure. As described above, the resonator
element 20 of the embodiment enables the Q value to be set high to
exhibit high performance by providing the recessed section 60 in the
electrode inside the long groove 30 between the compression region (the
first or the second region) and the extension region (the second region
or the first region).

[0051]FIG. 3 is a cross sectional view illustrating a featured part of a
resonator element according to a second embodiment of the invention. As
shown in FIG. 3, the resonating arm 24 includes recessed sections 60a
each in which the bottom surface of the long groove 30 is exposed, in the
second embodiment. Specifically, the recessed section 60a is formed when
the first exciting electrode 46 is formed inside the long groove 30 in a
manner such that the electrode is not formed as being partially removed.
The first exciting electrode 46 is formed by forming a Cr layer having a
high adhesiveness with a piezoelectric body as a lower layer, followed by
forming an Au layer that has a low electric resistance and is hardly
oxidized as an upper layer. As a result, the resonating arm 24 appears at
the bottom surface of the long groove 30. It is advisable that the
recessed section 60a is formed along the long groove 30, or at least
between a compression region and an extension region, i.e., at the root
portion of the resonating arm 24.

[0052]In the resonator element of the second embodiment, the recessed
section is provided to the film having thermal conductivity higher than
that of the material of the resonating body so as to cut off the heat
transfer path between the compression region and the extension region in
the film. As a result, only the long groove 30 functions as the heat
transfer path. Likewise the resonator element shown in FIGS. 1 and 2,
this structure causes the relaxation time to lengthen, lowering the
relaxation frequency. As a result, a high Q value can be attained.

[0053]FIG. 4 is a plan view illustrating a featured part of a resonator
element according to a third embodiment of the invention. As shown in
FIG. 4, the resonating arm 24 of the third embodiment is structurally
different from that of the first embodiment in that the first exciting
electrode 46 formed inside the long groove 30 has an end section 62 in
which the recessed section is not formed. Other structure is the same as
that of the resonator element 20 of the first embodiment.

[0054]In the resonator element of the third embodiment, the first exciting
electrode 46 is formed on the bottom surface, which corresponds to the
end section 62, of the long groove 30 of the resonating arm 24, and the
recessed section 60 is formed on the bottom surface, excluding the end
section 62 and a root section 61, of the long groove 30. In a plan view
of the long groove 30, the recessed section 60 is surrounded by the end
section 62 and the root section 61.

[0055]The recessed section 60a of the second embodiment can be applied to
the resonating arms of the third embodiment.

[0056]The resonator element of the third embodiment can lengthen the
relaxation time since the recessed sections 60 are provided to the
resonating arms 24. Further, the recessed section 60 is not formed, but
the electrode is formed at the end section of the long groove 30. This
structure can reduce ohmic losses (resistance losses) with assured
electric conduction.

[0057]FIGS. 5A and 5B are cross sectional views illustrating a featured
part of a resonator element according to a fourth embodiment of the
invention. As shown in FIGS. 5A and 5B, a resonating arm 24a of the
resonator element of the fourth embodiment has no long grooves.

[0058]The resonating arm 24a shown in FIG. 5A includes the recessed
sections 60 in an Au layer serving as the upper layer. The recessed
sections 60 are formed in the same manner of the first embodiment in the
step of forming the first exciting electrodes 46 on the surfaces of the
resonating body as films.

[0059]The resonating arm 24a shown in FIG. 5B includes the recessed
sections 60a in which the upper and lower layers are removed. The
recessed sections 60a are formed in the same manner of the second
embodiment in the step of forming the first exciting electrodes 46 on the
surfaces of the resonating body as films.

[0060]It is advisable that the recessed sections of the fourth embodiment
are formed at least between a compression region and an extension region,
i.e., at the root portion of the resonating arm 24a.

[0061]In the resonator element of the fourth embodiment, the recessed
section is provided to the film having thermal conductivity higher than
that of the material of the resonating body so as to cut off the heat
transfer path between the compression region and the extension region in
the film. As a result, only the long groove 30 functions as the heat
transfer path. Likewise the resonator element shown in FIGS. 1 and 2,
this structure causes the relaxation time to lengthen, lowering the
relaxation frequency. As a result, a high Q value can be attained.

[0062]FIG. 6 shows an oscillator in which the resonator element of the
invention is mounted.

[0063]An oscillator 200 according to a fifth embodiment of the invention
mainly includes the resonator element 20, an IC element 212, a package
210 housing the IC element 212 and the resonator element 20, and a lid
220 sealing an opening of the package 210.

[0064]The package 210 is box-shape-formed by layering and firing ceramic
green sheets and the like, and has a cavity formed in a recessed shape.
An inner mounting electrode 214 for mounting the resonating element 20 is
formed in the cavity. The package 210 is provided with external mounting
terminals on the outer bottom surface. The external mounting terminals
are electrically coupled to the inner mounting electrode 214 through
through-holes and the like (not shown).

[0065]The lid 220 seals the opening provided at the upper surface of the
package 210. The lid 220 can be made of metal or glass.

[0066]The IC element 212 and the resonator element 20 are mounted to the
package 210 thus structured. The IC element 212 is mounted by wire
bonding. The resonator element 20 is mounted with a conductive adhesive
216. The lid 220 is bonded with a bonding member to seal the opening of
the package 210 in which the IC element 21 and the resonator element 20
are mounted.

[0067]The oscillator thus structured can have a feature that the lowering
of a Q value caused by a heat transfer is prevented.